Cooling systems for sewing machine driving units

ABSTRACT

An electrically operated driving unit for a sewing machine is supported on the sewing machine in axial alignment with the main shaft of the sewing machine with which the driving unit is operatively connected. The flow of heat from the driving unit to a handwheel on the main shaft adjacent thereto is controlled by an insulated interposer between the driving unit and main drive shaft and by a fan associated with the handwheel for inducing a flow of air to cool the handwheel and the driving unit. Fan means included within a sealed electric motor forming a part of the driving unit also induces transfer of heat generated inside the motor to peripheral portions of the motor which are located within the influence of the air flow induced by the handwheel fan.

O United States Patent [151 3,667,41 3 Kleinschmidt et al. June 6, 1972 [54] COOLING SYSTEMS FOR SEWING 2,318,442 5 1943 Way ..310/66 MACHINE DRIVING UNITS P ma Ex J. D. Mill 72 Inventors: Johann 0. Kleinschmidt; Heinz E. Walter, 'i R Sk d er both of Blankenloch' Helmar 11 Hull u y Attorney-Marshall Jr Breen, Chester A. Williams, Jr. and Karlsruhe, all of Germany Robert E smith [73] Assignee: The Singer Company, New York, NY. [22] Filed: June 11, 1971 [57] ABSTRACT An electrically operated driving unit for a sewing machine is [2]] Appl' 1s2l39 supported on the sewing machine in axial alignment with the I main shaft of the sewing machine with which the driving unit is Cl 310/66 operatively connected. The flow of heat from the driving unit [51] Int.Cl. ..DOSb 69/00 to a ha dwh el n the main shaft adjacent thereto is con- [58] Field of Search ..3 10/5 2, 62, 60, 66, 68, 92, "oiled by an insulated interposer between the driving i and 310/93; 1 12/1 19 220 main drive shaft and by a fan associated with the handwheel for inducing a flow of air to cool the handwheel and the driv- [56] References cued ing unit. Fan means included within a sealed electric motor UNITED STATES PATENTS forming a part of the driving unitalso induces transfer of heat a generated inside the motor to peripheral portions of the motor 3,400,677 BOWCI'S ..1 A are located within the influence of the air flow induced 3,404,767 10/1968 Farnumm. ...1 12/219 A by the handwhee] f 3,407,910 10/1968 Heidt.... ...1 12/219 A 7 2,516,184 7/1950 Christie ..310/58 7 Claims, 7 Drawing figures 13 so 55 5 s3 4 7 47 I I 40 :6 l l as 56 i 34 I02 f lOl I00 50 U 5 4a 23 l FATENTEDJUN 6 I972 3, 667, 413 SHEET 1 OF 2 uquuuuuuu 73 lg. L

INVENTORS Johann Oflo Klelnschmidt,

Helnz Emll Walter, Helmor Heinz Holl WITNESS: I BY PATENTEDJUN 6 m2 SHEET 2 [IF 2 WITNESS:

COOLING SYSTEMS FOR SEWING MACHINE DRIVING UNITS BACKGROUND OF' THE INVENTION Electric motors have been arranged heretofore on an outboard extremity of a sewing machine main drive shaft and it has been known to arrange a handwheel closely adjacent to or as a part of such motors, but without any special insulation or cooling provisions. In many of the prior art constructions, heat dissipation did not present a problem because the prior art motors were appreciably larger in mass in proportion to the power generated than present day motors so that they inherently provided more ample heat dissipation; and many prior art devices were simply motors whereas the driving unit of the present invention may include in addition to a motor, power controlling and transmitting devices, as for instance, brake mechanisms which also generate heat.

Most-prior art'electric motors, moreover, are open to the atmosphere so that cooling air from outside the motor may be directed therethrough. To curtail damage caused by brush sparking, modern motors may be sealed and this presents a serious problem as to the manner in which heat which is generated in the motor armature might be dissipated.

SUMMARY OF THE INVENTION It is an object of this invention to provide an electrically operated sewing machine drive unitwhich is carried directly on a sewing machine casing and adjacent to the handwheel with means for controlling heat transfer from the drive unit to the handwheel so that the handwheel may be maintained within a temperature range which is comfortable for a sewing machine operator. This object is attained by the inclusion of an insulating interposer between the drive shaft of the driving unit and the sewing machine main shaft on which the driving unit and the handwheel are carried so that the transfer of heat to the handwheel by conduction is minimized; and by the provision of a ventilating system utilizing a fan associated with the handwheel for inducing a flow of cooling air across the handwheel and through air distributing ports in a support casing for the driving unit which directs the cooling air uniformly aboutthe periphery of the electric motor.

This invention has particular utility when used with a driving unit employing a low inertia electric motor of the type in which the armature is arranged in a sealed compartment. Attainment of the objects of this invention is furthered by the provision of centrifugal fan blades in association with the armature of-the low inertia electric motor within the sealed compartment serving to assist in the transfer of heat generated within the motor from the vicinity of the motor drive shaft-outwardly to the motor'casing and closely adjacent to the moving curtain of cooling air which is directed about the periphery of the electric motor.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view as will hereinafter appear, this invention will now be described in detail with reference to the accompanying drawings of a preferred embodiment in which:

FIG. 1 represents an elevational view of a sewing'machine with a driving unit applied directly thereon and having this invention applied thereto,

FIGLZ is an enlarged vertical cross-sectional view of the driving unit ofFIG. 1,

FIG. 7 is an exploded perspective view of the coupling elements of the sewing machine drive shaft and the driving unit together with the insulating interposer therebetween.

Referring to the drawings, FIG. 1 illustrates a conventional sewing machine including a frame with a work supporting bed 11, a standard 12 rising from the bed and a bracket arm 13 extending from the standard and overhanging the bed. The sewing machine is illustrated supported on a power table 14. The sewing machine is equipped with stitch forming instrumentalities of which the needle 15 is illustrated in FIG. 1, which stitch forming instrumentalities are actuated from a main shaft 16 journaled in the bracket arm l3of the sewing machine frame. The operative connections between the main shaft and the needle and other stitch forming instrumentalities may take any conventional form.

As illustrated in FIG. 1, a sewing machine direct driving unit, indicated generally at 20, is carried on the sewing machine frame above the power table 14. The driving unit 20 as is explained in detail below, may include ancillary mechanisms such as braking devices and the like, in addition to a motor means. A wiring harness 21 extends from the driving unit 20 to an electrical control panel 22 which may be arranged beneath the power table, the wiring harness may include control conduits as well as conductors for a power supply to the driving unit.

With reference to FIG. 2 of the drawings, the sewing machine frame at the juncture of the bracket arm 12 and standard 13 is formed with a seat 30 for accommodating the support means for the driving unit 20. Preferably, the seat 30 is formed with a clearance opening 31 into the interior of the sewing machine framev The sewing machine main shaft 16 extends through the clearance opening 31 and carries a coupling member 32 which is formed at its free end with a counterbore 33. The coupling member is secured to the sewing machine main shaft by a set screw 34 and by a headed screw 35 which is threaded axially into the sewing machine main shaft 16 and formed so as to abut the counterbore 33 in the coupling member. The free extremity of the coupling member 32 is formed of a plurality of spaced axially extending fingers 36 by which a driving connection with an electric motor is made, as will be described hereinbelow.

Accommodated on the seat 30 on the sewing machine frame is an inner flange 40 of a supporting casing 41 which is secured to the sewing machine frame by cap screws 42. The inner flange 40 is formed with a clearance opening 43 contiguous with the sewing machine frame clearance opening 31. A bell-shaped outer flange 44 formed on the supporting casing 41 is provided with a motor accommodating seat 45 and with clearance holes 46 for fastening screws 47 by which an electric'motor may be fastened thereto.

Secured as by set screws 50 to the coupling member 32 on the main shaft 16 of the sewing machine is a hub portion 51 of a handwheel 52. The handwheel is formed with a continuous rim 53 which is disposed within a circular cavity 54 inside the supporting casing 41. As shown in FIGS. 1 and 2, the supporting casing 41 is cut away as at 55 at the top portion thereof to expose a segment of the handwheel rim for ready access by the sewing machine operator. The rim 53 of the handwheel is preferably supported from the hub portion 51 by a plurality of evenly spaced spokes 56 which are preferably skewed radially and also inclined relatively to the axis of rotation of the handwheel so as to provide fan blades effective to move air in a direction from left to right as viewed in FIG. 2. The fan might also be provided by a member formed separately from the handwheel but operatively associated therewith to move air when the handwheel is turned.

The sewing machine frame is formed with an air inlet opening 60 through which air drawn by the fan provided by the handwheel spokes 56 may be drawn into the sewing machine frame. An air conduit is provided from the air inlet opening 60 to the fan through the openings 31 and 43 in the sewing machine frame and supporting casing, respectively. As shown in FIGS. 2 and 3, the outer flange 44 of the supporting casing 41 is formed with a plurality of radially skewed air conduits 61 each terminating in an air outlet port 62 at the outer periphery of the driving unit 20. When the sewing machine is in operation, therefore, the fan defined by the handwheel spokes will draw ambient air into the sewing machine frame over the sewing machine main shaft 16 through the handwheel and then in a circuitous path in close contact with the supporting casing 41 and in a plurality of divided streams about the supporting casing by the plurality of air outlet conduits 61 therein, and finally through the outlet ports 62 for distribution about the outer periphery of the driving unit.

Secured on the motor seat 45 of the supporting casing is an electric motor indicated generally at 70 and including a cylindrical housing 71 fitted at each end with circular end plates 72 each secured bybolts 73 to provide a substantially airtight compartment 74. Within the airtight compartment a motor shaft 75 is joumaled in bearings 76 in the end plates 72. An armature in the form of a disc 77 is made fast on the motor shaft within the airtight compartment and rotates therein relatively to a plurality of permanent magnets 78 supported on the end plates 72. Brushes 79 are also supported within the airtight motor compartment to contact electrical windings which may be printed or otherwise provided on the armature disc to provide a low inertia electric motor of the type which is disclosed and described in greater detail in US. Pat. No. 2,970,238, Jan. 31, 1961 of R. L. Swiggett to which reference may be had. At each side of the armature 77 a centrifugal air impeller 80 and 81 is secured as by set screws 82. The impellers serve to maintain the circulation of the air within the airtight motor compartment during operation of the motor so as to influence transfer of heat generated within the motor compartment to the cylindrical housing 71 of the motor. Exteriorly of one end plate 72 of the electric motor 70 and within the supporting casing 41, a brake disc 90 with a surface 91 of high friction material is secured to the motor shaft 75. Axially shiftable on guide pins 92 secured in the end plate 72 of the electric motor is a brake shoe 93 which is preferably constructed as an electro-magnet which when energized will be drawn into braking engagement with the friction surface 91 on the brake disc 90. Coil springs 94 on the guide pins 92 serve tourge the brake shoe 93 out of braking engagement when the electro-magnet is deenergized.

Within the supporting casing 41 the electric motor shaft 75 carries a coupling member 100 which is preferably shaped in a fashion similar to that of the coupling member 32 on the sewing machine main shaft 16. The coupling member 100 thus includes axial fingers 101 which are arranged interdigitated with the fingers 36 of the coupling member 32 to define a driving connection between the motor shaft and the sewing machine main shaft. As shown in FiG. 4, the interdigitated fingers 36 and 101 occupy only a fraction of the circumference of the coupling members. A disc 102, of heat insulating material such as rubber or the like is interposed between the coupling members 32 and 100 and as shown in FIGS. 4 and 7 the disc 102 is formed with radial teeth 103 which extend between the interdigitated fingers 36 and 101 and fill the circumferential space therebetween.

The free extremity of the driving unit 20 accommodates a cover member 1 which may shield devices such as speed or position sensing mechanisms which do not form a direct part of the present invention.

OPERATION The heat which is generated by the operation of the electric motor 70 and by the operation of the brake shoe 93 if transferred to the handwheel 52 might provide a source of discomfort and annoyance for the sewing machine operator. The construction described in detail above effectively minimizes the heat transfer to the handwheel and also minimizes objectionable temperature rise of the supporting casing 41 which might be touched by an operator during manipulation of the handwheel 52. This is accomplished by the two-fold approach of first minimizing transfer of heat to the handwheel by conduction through the sewing machine main shaft 16 by the provision of the heat insulating interposer 102 between the motor shaft of the sewing machine main shaft. Second and concurrently, a ventilation system is provided by the provision of a fan in association with the handwheel 52 and an arrangement of air conduits designed to provide for a flow of cooling air through the handwheel along the supporting casing and in a path across the outer periphery of the electric motor. Moreover, heat transfer within the electric motor is encouraged toward the outer periphery thereof by the centrifugal impellers within the heat motor compartment. As a result, a totally enclosed electric motor may be operated at heavy load without developing temperature levels which would be damaging to the motor. Moreover, the handwheel without objectionable temperature rise may be advantageously located closely adjacent to an electric driving unit for the sewing machine which is carried directly on the sewing machine frame.

Having set forth the nature of this invention, what is claimed herein is: i

1. In a sewing machine having a frame with a main shaft joumaled therein, an electrically operated driving unit including an electric motor having a housing, a motor shaft journaled in said housing, means for securing said electric motor housing to said sewing machine frame, a handwheel carried on said main shaft between said sewing machine frame and said electric motor housing, and coupling meanspperatively interconnecting said motor shaft and said main shaft, cooling means characterized by a heat insulating member interposed between said motor shaft and said main shaft to minimize conduction of heat from said electric motor through said sewing machine main shaft to said handwheel, a fan operatively associated with said handwheel, an air inlet conduit leading to said fan, and an air outlet conduit leading from said fan to an air outlet port arranged to direct cooling air across said electric motor housing.

2. In a sewing machine as set forth in claim 1 in which said fan is defined by air impelling blades extending as spokes between a hub portion and a rim portion of said handwheel.

3. In a sewing machine as set forth in claim 2 in which said means for securing said electric motor housing to said sewing machine frame comprises a supporting casing arranged.

therebetween, said supporting casing being formed with a peripheral opening exposing the rim portion of said handwheel, and in which said air outlet conduit and air outlet port are formed on said supporting casing.

4. In a sewing machine as set forth in claim 3 in which said supporting casing is formed with a plurality of air outlet conduits each radially skewed and each leading to an individual air outlet port adjacent to said electric motor.

5. In a sewing machine as set forth in claim 1 in which said motor shaft and said main shaft are axially aligned and in which said coupling means operatively connecting said motor shaft and said main shaft comprises a pair of collars of like diameter each secured to one of said shafts, interdigitated fingers formed on said pair of collars, said fingers together occupying only a fraction of the circumference of said collars, and in which said heat insulating member comprises a disc formed with radial teeth, said insulating member teeth extending between the interdigitated fingers of said pair of collars and filling that fraction of the circumference not occupied by said interdigitated fingers.

6. In a sewing machine as set forth in claim 1 in which said electric motor housing includes a substantially airtight compartment, an armature on said motor shaft within said airtight compartment, and in which a centrifugal impeller is carried for rotation with said armature within said airtight compartment to encourage heat transfer toward the outer periphery of said electric motor housing.

7. In a sewing machine as set forth in claim 6 in which said electric motor armature comprises a substantially solid disc carrying electrically conductive windings thereon, and in which a pair of impellers are secured on each side of said armature disc. 

1. In a sewing machine having a frame with a main shaft journaled therein, an electrically operated driving unit including an electric motor having a housing, a motor shaft journaled in said housing, means for securing said electric motor housing to said sewing machine frame, a handwheel carried on said main shaft between said sewing machine frame and said electric motor housing, and coupling means operatively interconnecting said motor shaft and said main shaft, cooling means characterized by a heat insulating member interposed between said motor shaft and said main shaft to minimize conduction of heat from said electric motor through said sewing machine main shaft to said handwheel, a fan operatively associated with said handwheel, an air inlet conduit leading to said fan, and an air outlet conduit leading from said fan to an air outlet port arranged to direct cooling air across said electric motor housing.
 2. In a sewing machine as set forth in claim 1 in which said fan is defined by air impelling blades extending as spokes between a hub portion and a rim portion of said handwheel.
 3. In a sewing machine as set forth in claim 2 in which said means for securing said electric motor housing to said sewing machine frame comprises a Supporting casing arranged therebetween, said supporting casing being formed with a peripheral opening exposing the rim portion of said handwheel, and in which said air outlet conduit and air outlet port are formed on said supporting casing.
 4. In a sewing machine as set forth in claim 3 in which said supporting casing is formed with a plurality of air outlet conduits each radially skewed and each leading to an individual air outlet port adjacent to said electric motor.
 5. In a sewing machine as set forth in claim 1 in which said motor shaft and said main shaft are axially aligned and in which said coupling means operatively connecting said motor shaft and said main shaft comprises a pair of collars of like diameter each secured to one of said shafts, interdigitated fingers formed on said pair of collars, said fingers together occupying only a fraction of the circumference of said collars, and in which said heat insulating member comprises a disc formed with radial teeth, said insulating member teeth extending between the interdigitated fingers of said pair of collars and filling that fraction of the circumference not occupied by said interdigitated fingers.
 6. In a sewing machine as set forth in claim 1 in which said electric motor housing includes a substantially airtight compartment, an armature on said motor shaft within said airtight compartment, and in which a centrifugal impeller is carried for rotation with said armature within said airtight compartment to encourage heat transfer toward the outer periphery of said electric motor housing.
 7. In a sewing machine as set forth in claim 6 in which said electric motor armature comprises a substantially solid disc carrying electrically conductive windings thereon, and in which a pair of impellers are secured on each side of said armature disc. 